Human exposure to chemicals is rarely limited to one single chemical. Recent concern about groundwater contamination in agricultural areas has led the NTP To initiate a study of the toxicology of pesticide/fertilizer chemical mixtures which are based on confirmed groundwater contamination in California and Iowa. While the long-term toxicity studies were being done on contract, specific myelotoxicity and residual effects of bone marrow were investigated. Bone marrow parameters were monitored in mice exposed to 0, 1X, 1OX, and 100X of chemical mixture II or III drinking water for 3 to 15 weeks. Some mice were allowed to recover for 8 weeks after cessation of chemical treatment, then Received whole body irradiation 200 rads twice at 8-week intervals. Examinations of hematology and histopathology were also performed.